Polychromophoric heterocyclic ultraviolet stabilizers

ABSTRACT

The invention relates to bichromophoric heterocyclic ester compounds which have been found to be effective ultraviolet stabilizers. The invention also relates to ultraviolet degradable organic compositions containing a stabilizing amount of these bichromophoric heterocyclic ester compositions to prevent such degradation. These stabilizers are effective in the presence of other additives commonly employed in polymeric compositions including, for example, pigments, colorants, fillers, reinforcing agents and the like. These ultraviolet stabilizers may also be incorporated into the organic compositions in the polymer melt or dissolved in the polymer dope, coated on the exterior of the molded article, film or extruded fiber.

This invention relates to bichromophoric heterocyclic ester ultravioletstabilizers and their use in organic compositions. More particularly,the invention relates to bichromophoric heterocyclic ester compositionsand the stabilization of ultraviolet degradable organic compositionsagainst deterioration resulting from the exposure to such radiationswith such bichromophoric heterocyclic ester compositions.

The degradative effects of ultraviolet light on various organiccompositions is well known in the art. The photo-deterioration ordegradation is of particular concern with organic photo-degradablecompositions which are exposed to ultraviolet light, such as sunlight,for long periods of time. One group of such photo-degradable organiccompositions are polymeric compositions such as polyolefins, polyestersand the like. On exposure to sunlight for extended periods of time,these polymeric compositions degrade and their physical properties arereduced to render the polymeric composition less useful for mostapplications. Therefore, considerable effort has been directed toproviding a solution to the photo-degradation problem of polymericcompositions. As a result of this effort, there have been discoveredmany additives and stabilizers which improve the stability of polymericcompositions.

Moreover, various additives and stabilizers exhibit the power to absorbultraviolet radiation within the band of 2900 to 4000 A. and, whenincorporated in various plastic materials such as transparent sheets,the resultant sheet acts as a filter for all the radiation passingthrough and will transmit only such radiations as are not absorbed bythe sheet and/or the absorbing agent. It is thus possible to screen outundesirable radiations and utilize the resulting transparent sheet as afilter in many technical and commercial applications, such as wrappingsfor food products and the like.

While there are many additives, stabilizers and mixtures thereof whichare known in the art to improve the ultraviolet light stability oforganic compositions, there is a need in the art for more efficient andeffective stabilizers to prevent the photo-degradation of organiccompositions susceptible to photo-degradation. Therefore, to provide amore effective and efficient ultraviolet stabilizer for organiccompositions susceptible to such degradation would be an advance in thestate of the art.

It is, therefore, an object of the present invention to provide moreeffective and efficient ultraviolet light stabilizer compositions.

Another object of the present invention is to provide usefulcompositions characterized by improved resistance to ultravioletdegradation and deterioration.

It is still another object of the present invention to providecompositions containing bichromophoric compositions which are resistantto ultraviolet degradation.

It is a still further object of this invention to provide processes forimproving the resistance of organic materials to deterioration anddegradation by actinic radiation and especially ultraviolet radiation.

It is a still further object of this invention to provide compositionsand processes for improving the resistance of organic materials todeterioration and degradation by actinic radiations, including shortwave-length visible radiations.

Further objects and advantages of the invention will be apparent tothose skilled in the art from the accompanying disclosure and claims.

In accordance with the present invention, bichromophoric heterocyclicester compositions are provided which are useful as ultraviletstabilizers or ultraviolet screening agents. These organic compositionscontain at least one heterocyclic group containing composition connectedthrough a carboxyl group to an aromatic ring which, upon exposure toultraviolet light, may undergo the "photo-Fries" rearrangement. Thepolychromophoric compositions of the present invention have thefollowing structure:

    (A).sub.x --C

wherein A is a group having the structure: ##STR1## wherein X and Y area carbon atom, a carbon atom containing an R group, or a nitrogen atom;

Z is an oxygen atom, a sulfur atom, a nitrogen atom, a nitrogen atomcontaining a hydrogen atom or a substituted or unsubstituted lower alkylgroup having 1 to 12 carbon atoms;

R, R₁, R₂, R₃, R₄ and R₅ are hydrogen, lower alkyl, substituted loweralkyl, cycloalkyl, substituted cycloalkyl, aryl, halogen, substitutedaryl, lower alkylaryl, aryl-substituted-aryl, alkoxy, carboxy, nitrile,and the substituents R₁ and R₂, R₂ and R₃, and R₃ and R₄, combined withthe carbon atoms to which they are attached, are joined alkylene groupscompleting a carboxylic ring which can be substituted with any of thesubstituents listed above for R₁, R₂, R₃ and R₄.

I is a substituent listed above for R₁, R₂, R₃ and R₄ and is present onall positions of the benzenoid ring, except the carbon atom attached tothe heterocyclic ring and the carbon atom attached to the carboxyl groupconnecting the heterocylic aromatic A group with the aromatic C group.At least one I substituent on one of the carbon atoms adjacent to thecarbon atom attached to the carbonyl group is hydrogen and the remainingI substituents can all be the same or different.

x is an integer of 1 to 4; and

C is:

(a) an aromatic group having the formula ##STR2## where I is the samesubstituent as listed above and is present in all positions of thebenzenoid ring except the carbon atom attached to the carbonyl groupconnecting the A and C moieties, and said I substituents can all be oneof the substituents listed above or different listed substituents;

(b) an alkyl group or hydrogen; and

(c) an aromatic group having the formula ##STR3##

Suitable A groups having the structure ##STR4## are, for example,substituted and unsubstituted benzoxazoles, benzotriazoles,benzothiazoles, and benzimidazoles.

Examples of such suitable benzoxazole moieties are those having theformula ##STR5## such as 2-(4-methylphenyl)-5-benzoxazolecarboxylate,2-(3-methylphenyl)-5-benzoxazolecarboxylate,2-(4-chlorophenyl)-5-benzoxazolecarboxylate,2-(4-dimethylaminophenyl)-5-benzoxazolecarboxylate,2-(4-t-butylphenyl)-5-benzoxazolecarboxylate,2-(4-methoxyphenyl)-5-benzoxazolecarboxylate,2-(4-methylphenyl)-6-methyl-5-benzoxazolecarboxylate,2-(4-chlorophenyl)-6-methyl-5-benzoxazolecarboxylate,2-(4-methylphenyl-6-chloro-5-benzoxazolecarboxylate, and2-(4-methylphenyl)-6-t-butyl-5-benzoxazolecarboxylate.

Examples of suitable benzotriazole moieties are those having the formula##STR6## such as 2-(4-methylphenyl)-5-benzotriazolecarboxylate,2-(4-chlorophenyl)-5-benzotriazolecarboxylate,2-(4-dimethylaminophenyl)-5-benzotriazolecarboxylate,2-(3-methylphenyl)-5-benzotriazolecarboxylate,2-(2-methylphenyl)-5-benzotriazolecarboxylate, and2-(4-t-butylphenyl)-5-benzotriazolecarboxylate.

Examples of suitable benzothiazole moieties are those having the formula##STR7## such as 2-(4-methylphenyl)-5-benzothiazolecarboxylate,2-(4-chlorophenyl)-5-benzothiazolecarboxylate,2-(3-methoxyphenyl)-5-benzothiazolecarboxylate,2-(4-methylphenyl)-6-chloro-5-benzothiazolecarboxylate, and2-(4-chlorophenyl)-6-methyl-5-benzothiazolecarboxylate.

Examples of suitable benzimidazole moieties are those having the formula##STR8## wherein Q is hydrogen or a substituted or unsubstituted loweralkyl group containing 1 to 12 carbon atoms such as 2-(4-methylphenyl)-5-benzimidazolecarboxylate,2-(4-chlorophenyl)-5-benzimidazolecarboxylate,2-(4-methylphenyl)-6-benzimidazolecarboxylate,2-(4-methoxyphenyl)-5-(N-ethylbenzimidazole)carboxylate, and2-(4-methoxyphenyl)-6-chloro-5-(N-methylimidazole)carboxylate.

Examples of suitable indole moieties are those having the formula##STR9## wherein Q is hydrogen or a substituted or unsubstituted loweralkyl containing 1 to 12 carbon atoms, such as2-(4-methylphenyl)-5-indolecarboxylate,2-(4-chlorophenyl)-5-indolecarboxylate,2-(3-methylphenyl)-6-indolecarboxylate,2-(4-methylphenyl)-6-chloro-5-indolecarboxylate,2-(4-methylpheny)-5-N-methylindole)carboxylate, and2-(4-chlorophenyl)-6-methyl-5-(N-ethylindole)carboxylate.

Suitable C groups are those which are

(a) an aromatic group having the formula ##STR10## where I is the samesubstituent as listed above and is present in all positions of thebenzenoid ring except the carbon atom attached to the carbonyl groupconnecting the A and C moieties, and said I substituents can all be oneof the substituents listed above or different listed substituents;

(b) an aromatic group having formula ##STR11##

The bichromophoric heterocyclic ester compositions can be prepared byreacting an acid chloride with a phenol. For example, one group of suchorganic compounds useful as ultraviolet stabilizers is, for example,compositions having the following structures ##STR12##

One method for preparing these compounds is by the following procedure:##STR13##

It is necessary that at least one carbon atom adjacent to the carbonatom attached to the carboxy oxygen contain a hydrogen substituent sothat on exposure to ultraviolet light, the aryl ester is capable by the"photo-Fries" rearrangement of forming a phenol group in that positionformerly joined through an oxygen atom to the carbonyl linking group, asfor example: ##STR14##

The acid chlorides were prepared by reaction of the corresponding acid[See Zh. Obshch. Khim., 38, 100 1-5 (1968); Chem. Abstr. 69 96568(1968)] with freshly distilled thionyl chloride [See J. Chem. Soc. 101,2476 (1912)]. The phenols were obtained from commercial sources, or wereprepared by standard methods; a critical requirement is that one of thepositions adjacent the phenolic hydroxyl group be unsubstituted.

The heterocyclic compositions can be added to organic compositions whichare susceptible to ultraviolet degradation. Such compositions include,for example, polymeric compositions such as polyester fiber and moldingcompositions, such as polyethlene terephthalate, poly(tetramethyleneterephthalate) and the like; polyolefins such as, for example, high,medium and low density polyethylene, polypropylene, polybutene and thelike; polyamides such as nylon 6, nylon 66, N-methoxymethylpolyhexamethylene adipamide and the like; polycarbonates; polyvinylchlorides and copolymers; cellulose esters; acrylic/butadiene/styreneplastic; polyacrylics such as methyl methacrylate; polystyrene; gelatin;vinylidene chloride copolymers such as vinylidene chloride/vinyl acetatecopolymers; ethylene vinyl acetate copolymers; cellulose ethers such asmethyl cellulose; polyvinyl esters such as polyvinyl acetate;polyethylene oxide; polyvinyl acetals, polyformaldehydes; andpolyurethanes. Such compositions also include natural and syntheticrubbers, such as polybutadiene, and unsaturated organic compositionssuch as oils and the like, as well as compositions containing suchorganic compositions.

The bichromophoric compositions, as effective ultraviolet stabilizers orscreening agents, are generally used in an amount of from 0.01 to 10%,by weight, based on the weight of the organic material to which they areadded. While a detectable amount of ultraviolet screening andstabilization may be obtained with amounts less than 0.01%, this amountof stabilization or screening would be of little practical utility in acommercial application. Moreover, while amounts greater than 10%, byweight, provide effective ultraviolet stability and screening, suchconcentrations are undesirable because of cost and the deleteriouseffect which such concentrations may have on the mechanical propertiesof the organic composition in which the stabilizer is incorporated.Preferably, the stabilizer is used in an amount of from about 0.1 toabout 3%, by weight. For example, an amount of 2%, by weight, of thestabilizer effectively stabilizes cellulose acetate butyrate andpolyester such as poly(tetramethylene terephthalate) plasticcompositions.

The ultraviolet stabilized organic compositions of the present inventionmay also contain other additives, pigments, colorants, stabilizers andthe like. For example, polymeric compositions, such as polyolefins, mayalso contain and generally do contain other additives such as white orcolored pigments or colorants, antioxidants, plasticizers, flow aids,processing aids, polymeric modifiers and the like.

These novel bichromophoric ultraviolet stabilizers may be incorporatedinto organic compositions by melt-blending or may be added onto thesurface of an organic plastic material prior to being molded into asuitable object. These materials can also be added to coatings and thelike which can be applied to the surface of a molded object.

This invention will be further illustrated by the following examplesalthough it will be understood that examples are included merely forpurposes of illustration and are not intended to limit the scope of theinvention.

EXAMPLE 1 Methyl 2-(4-methylphenyl)-5-benzoxazolecarboxylate (1a) can beprepared by the following procedure

The condensation (and subsequent cyclization) of methyl4-hydroxy-3-aminobenzoate with p-toluoyl chloride, offered a startingmaterial for the synthesis of a series of bichromophoric stabilizers inwhich the energy sink is attached directly to the benzoxazole moiety.

EXAMPLE 2 2-(4-Methylphenyl)-5-benzoxazolecarboxylic Acid

A solution containing 16.0 g. (0.06 mole) of methyl2-(4-methylphenyl)-5-benzoxazolecarboxylate (1a), 4.0 g. (0.1 mole) ofsodium hydroxide, and 50 ml. of water in 275 ml. of ethanol was stirredat 25° for 16 hours. The reaction mixture was poured into 1 l. of water.Acidification gave a white precipitate which was filtered, washed withwater, and when air-dried amounted to 14.44 g. (95%) of2-(4-methylphenyl)-5-benzoxazolecarboxylic acid (1b). The ir and nmrspectra were consistent with the proposed structure.

Anal. Calcd. for C₁₅ H₁₁ NO₃ (253.26): C, 71.14; H, 4.38; N, 5.53.Found: C, 70.68; H, 4.37; N, 5.41.

EXAMPLE 3 2-(4-Methylphenyl)-5-benzoxazolecarbonyl Chloride (1c)

2-(4-Methylphenyl)-5-benzoxazole carboxylic acid (13.0 g., 0.05 mole)was heated in 50 ml. of thionyl chloride (containing 10 drops of DMF)for 20 hours. The excess SOCl₂ was removed by a nitrogen sparge leavinga white solid. This was recrystallized from toluene to give 12.95 g.(95%) of 2-(4-methylphenyl)-5-benzoxazolyl chloride (1c). The ir and nmrspectra were consistent with the proposed structure.

EXAMPLE 4 Phenyl 2-(4-Methylphenyl)-5-benzoxazolecarboxylate (1d)

A solution containing 4.43 g. (0.016 mole) of2-(4-methylphenyl)-5-benzoxazolecarbonyl chloride in 50 ml. or methylenechloride was added dropwise to a solution containing 1.88 g. (0.02 mole)of phenol and 0.80 g. (0.02 mole) of sodium hydroxide in 25 ml. ofwater. After stirring at 50° for 20 hours, the layers were separated andthe organic layer was dried (MgSO₄) and concentrated to give 2.9 g.(54%) of 1d: UV (CH₂ Cl₂) λmax 306 nm (18,200), ε₃₂₅ = 3500.

Anal. Calcd. for C₂₁ H₁₅ NO₃ (329.36): C, 76,58; H, 4.59; N, 4.25.Found: C, 76,39; H, 4.95; N, 4.12.

EXAMPLE 5 4-Benzoyl-3-hydroxyphenyl2-(4-Methylphenyl)-5-benzoxazolecarboxylate (1e)

A solution containing 5.42 g. (0.02 mole) of 1c, 4.28 g. (0.02 mole) of2,4-dihydroxybenzophenone, and 0.8 g. (0.02 mole) of sodium hydroxide in50 ml. of chloroform and 15 ml. of water was refluxed for 3 hours. Aftercooling, the layers were separated and the organic layer wasconcentrated to given 5.27 g. (59%) of 1e as a white crystalline solid:UV (CH₂ Cl₂) λmax 306 nm (31,000), ε₃₂₅ =18,500.

Anal. Calcd. for C₂₈ H₁₉ NO₅ (449.47): C, 74.82; H, 4.26; N, 3.12.Found: C, 74.50; H, 4.25; N, 3.30.

EXAMPLE 6 m-Phenylene bis[2-(4-Methylphenyl)-5-benzoxazolecarboxylate](1f)

A mixture of 1c (5.42 g. 0.02 mole), resorcinol (1.10 g., 0.02 mole),and sodium hydroxide (0.8 g., 0.02 mole) was refluxed for 3 hours in amixture of chloroform (50 ml.) and water (15 ml.). Upon cooling a solidseparated between the layers which was filtered, air-dried, and amountedto 2.43 g. (42%) of 1f. UV (CH₂ CH₂) λ max 306 nm (52,000), ε₃₂₅ =13,000.

Anal. Calcd. for C₃₆ H₂₄ N₂ O₂ (580.61): C, 74.47; H, 4.17; N, 4.82.Found: C, 72.91; H, 4.14; N, 4.71.

These polychromophoric compositions find particular utility asultraviolet stabilizers in organic compositions requiring ultravioletstability. Such compositions include polymeric compositions such as, forexample, polyester fiber and molding compositions, poly-α-olefins,polyamides, acrylics, cellulose esters and the like, as well as moldedor shaped articles, film and coatings formed from such materials and thelike. Such compositions also include natural and synthetic rubbers, suchas natural rubber, as well as organic materials such as oils, fats, andunsaturated organic materials and materials having such materialscontained therein such as paints, varnishes, cosmetics and the like.

Weathering data results shown in Table I illustrate the stabilizationobtained with the compounds of this invention.

                  Table I                                                         ______________________________________                                        Weathering of Poly(tetramethylene terephthalate)                              Containing 0.5% of Various Stabilizers                                                        Flatwise Impact Strength                                                      After Mercury Lamp                                                            Exposure for Hours                                                            Indicated, Ft.-Lbs./In..sup.2                                 ______________________________________                                        Additive (0.5%).sup.a                                                                            0       300      500                                       ______________________________________                                        None              19        1        1                                        Methyl-2-(4-Methylphenyl)-5-                                                                    19        8        1                                        benzoxazolecarboxylate                                                        Phenyl-2-(4-Methylphenyl)-5-                                                                    19       15       10                                        benzoxazolecarboxylate                                                        4-Benzoyl-3-hydroxyphenyl-                                                                      19       18       18                                        2-(4-methylphenyl)-5-benz-                                                    oxazolecarboxylate                                                            m-Phenylene bis[2-(4-methyl-                                                                    19       18       10                                        phenyl)-5-benzoxazole                                                         carboxylate                                                                   ______________________________________                                         .sup.a Additives were incorporated by blending the powdered stabilizer an     granulated polymer followed by extrusion, pelletization and injection         molding into 1/16 × 1/2 × 2 1/2 in. flat bars. Flatwise impac     strength were determined by ASTM Procedure D256-56 Method A.             

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention.

We claim:
 1. A polychromophoric compound having the formula:

    (A).sub.x --C

where A is a group having the structure ##STR15## wherein R₁, R₂, R₃, R₄and R₅ are hydrogen, chloro, bromo, fluoro, lower alkyl, cycloalkyl,phenyl, lower alkylphenyl, phenyl-substituted-phenyl, alkoxy, phenoxy,dilower alkyl substituted amino, cyano, carboalkoxy and the substituentsR₁ and R₂, R₂ and R₃, and R₃ and R₄, combined with the carbon atoms towhich they are attached, are joined alkylene groups completing acarbocyclic ring, which ring can also be substituted with one or more ofthe substituents listed above for R₁, R₂, R₃ and R₄ ; I is the same asR₁, R₂, R₃ and R₄ and is present on all positions of the benzenoid ring,except the carbon atom attached to the heterocyclic ring and the carbonatom attached to the carbonyl group connecting the heterocyclic aromaticA group with the aromatic C group, at least one I substituent on one ofthe carbon atoms adjacent to said carbon atom attached to said carbonylgroup is hydrogen and said remaining I substituents can all be the sameor different; x is an integer of 1 to 4; and C is:a. an aromatic grouphaving the formula ##STR16## where I is the same substituent as listedabove and is present in all positions of the benzenoid ring except thecarbon atom attached to the carbonyl group connecting the A and Cmoieties, and said I substituents can all be one of the substituentslisted above or different listed substituents; or b. an aromatic grouphaving the formula ##STR17##
 2. A compound according to claim 1 havingthe formula ##STR18## wherein R₁, R₂, R.sub. 3, R₄ and R₅ are hydrogen,chloro, bromo, lower alkyl, cycloalkyl, phenyl, lower alkyl phenyl,alkoxy, phenyloxy, diloweralkyl substituted amino, and cyano,carboalkoxy, and the substituents R₁ and R₂, R₂ and R₃, R₃ and R₄,combined with the carbon atoms to which they are attached, are joinedalkylene groups completing a carbocyclic ring, which ring can also besubstituted with one or more of the substituents listed above for R₁,R₂, R₃ and R₄ ;I is the same as R₁, R₂, R₃ and R₄ and is present on allpositions of the benzenoid ring, except the carbon atom attached to thecarbonyl linking substituent, at least one of said I substituents on thecarbon atom adjacent to said carbon atom attached to said carbonyl groupis hydrogen and the remaining I substituents can all be one of thesubstituents listed above or different listed substituents.
 3. Acompound according to claim 2 having the formula: ##STR19##
 4. Acompound according to claim 2 having the formula: ##STR20##
 5. Acompound according to claim 2 having the formula ##STR21##
 6. A compoundaccording to claim 2 having the formula: ##STR22##
 7. A compoundaccording to claim 2 having the formula: ##STR23##
 8. A compoundaccording to claim 2 having the formula: ##STR24##